Just to round this off with a happy ending
The Vredestein didn't happen - took it in for the appt this morning at 11:30 and the tyres hadn't been delivered yet.
Man said he couldn't contact supplier as closed on Saturday - would ring me when they came in but warned could be Monday
2:30 came around - still no news so rang them back. Oops, said the man, he forgot to ring me - had managed to contact their supplier who said they couldn't get any Vredestein by today and probs not Monday either but could offer a very reasonable alternative that might be there by Monday.
So cancelled whole shebang - hopeless service ... if they knew they didn't have the tyres why the f@~ck didn't they let me know and save me driving in
Took the car to the local Kwik Fit just round the corner and asked them what they could get by Monday - but could they first give the tyres a once over.
Absolutely clean bill of health all round so no tyres needed - the original 'advisory' comment (which came from the latest MOT at the dealership) was erring on the side of caution in the extreme. Also my tread depth measuring skills clearly fell short, front were actually a good 4mm.
So all in all, an annoying day and some time wasted this week ... but in the end saved myself over £300
(or at least deferred til after Winter)